This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. During the reporting period, we have shown that targeting the CD28/CD80/CD86 and CD40/CD154 costimulatory pathways, by using LEA29Y and Chi220, prolongs allograft survival in rhesus macaques. Based on these results, we investigated the effects of CTLA4Ig and 3A8, which likewise inhibit the CD28/CD80/CD86 and CD40/CD154 pathways, respectively. All recipients in this cohort had immediate allograft function with normalization of fasting blood sugars and prolonged allograft survival, showing costimulation blockade-based regimens continue to yield success in islet transplantation. After transitioning to a new diabetes induction model with the use of streptozocin, experiments began to determine the optimal islet mass and anatomic site for islet transplantation. One animal was transplanted with15,000IE/kg of allogeneic islets intramuscularly into the trapezius and latissimus dorsi muscles with moderate success. In this report period, no further islet mass or anatomic site experiments have been done due to the desire for a more optimal biologic immunosuppressive regimen. In search of a more clinically relevant, less toxic regimen, anti-LFA-1 mAb and belatacept alone, resulted in immediate reversal of diabetes and islet survival for 367, 223, 373, 73 and 269 days. This biologic regimen promises to be a clinically relevant, tolerable regimen with potential for translation into the clinic. Additionally, we have further investigated the use of 3A8, a non-depleting mouse monoclonal antibody targeting CD40. Animals transplanted allogeneic islets under cover of 3A8, basiliximab and sirolimus had graft survivals of 155, 312, 208, 120, 45 days, establishing the potential of blocking the CD40 pathway in a non-depleting fashion in transplantation. Future plans include the testing of recombinant anti-CD40 antibodies for better characterization of CD40-blockade in our islet model and transplantation, and using anti-CD40-based biologic regimens to establish preclinical data for translation into the clinic.